Fabulous stuff that, Tiahaar! But know this: Thrust SSC was steered via a computer, just like modern fighter planes are. A modern fighter plane would not be flyable by a human, even if it were equipped with mechanical controls. Never mind the actuating forces required to move the control surfaces at today's speeds. It is about maintaining control over an inherently unstable mechanism. In common automotive terms, these vehicles will oversteer at the drop of a hat. Or in Nascar terms, they are extremely loose. Only a computer can react fast enough and precicely enough to keep them from spinning out. Fighter planes are designed that way because it makes them very nimble and able to perform quick evasive maneuvers. But this is possible only thanks to the computer. Noble and Green had this technology available to them, so they used it.

By all means, build bikes like that, and we'll play with them! Peter probably already has something like it, I would bet.

Tiahaar wrote:Wow interesting steering for sure on those two 'bents. Elliot! Question for you in particular and others in general: ever come across a rear-steer/front drive bike? Once upon a time I sketched out one I thought would be rideable and handle properly (had a positive rake fork on the rear with underseat steering). But I never built it (yet). THEN I ran across this fascinating page about RWSB contraptions: RearWheelSteerBikes, even has a photo of the playa with the Force car and Flatmo of KSR fame.

SO! I will attempt a rear-wheel-steer bike to bring and add to the bait/gimmick bike collection.

In the 60's part of a job was for me to drive a rear steering platfrom lift..
It was a trip to learn.. You stood up to drive.. The floor was a dead mans switch.. It had a steering wheel with a spinner knob.. All other controls were operated with the right foot

I might add that at cruising speeds bicycle steering is largely accomplished using the gyroscopic precession principle, as in you use the spinning wheelâ€™s forces to lean the bike in and out of turns (see http://en.wikipedia.org/wiki/Precession ). Motorcyclists are most familiar with it as the effect called â€˜counter-steerâ€™, the way you turn the handlebars AWAY from the direction you want to go to initialize the turn. That starts the lean of the bike into the turn. You then pull out of the turn by turning a bit sharper to bring the bike back upright.

The rear-wheel-steer bike has to be designed so that this gyroscopic torque helps it to come in and out of a turn in an intuitive way or else you are merely building a suicide machine

Awwwww, I would not build anything that was difficult to steer, would I???

This was my first build. It steered around a vertical axis behind the front wheel -- essentially hinged in the middle. I simply used two sturdy door hinges -- you can readily see the lower one in front of our feet. I knew it was wrong, but I figured it would be OK at our low speeds.

Well... that thing would jack-knife at one or two MPH if I wasn't right on top of it every instant. I finally dismantled it before somebody got hurt. (But I still have the front wheel, and it shall be rebuilt!)

HA! Awesome! Wish I'd been doing the Ventura KSR race that year to see it in action! The irony you realize of course is that your amazing monster trike likely would have been perfectly stable if peddled backwards...as a rear-wheel-steer

It is a relief to me to read that stuff. I have been frustrated and embarrased for many years because I cannot seem to fully grasp the physics of steering. Now I'm learning that I am not alone -- lots of perfectly competent people struggle with it!

I don't remember what I raced in Corvallis in 2007, but I sure Aced that sand in 2009, on the Pear County Chopper Trike (a.k.a. the NuVinci Flyer)! Now, the Mud.... I have yet to get thru the Corvallis Mud Pit.

most of which can be airily ignored for the purposes of crazy playa bikes

Damn you Tiahaar, I'll get ya for this.. Been up sence 4:00 this morning trying to make the steering design.. It's wont get out of my head..Like when a song sticks.. Went to the parts shed for some flea market stuff.. Ended up wasting two hours mocking up a bike frame and extention bars..

Anyway, The down tube of a stepthru trick bike makes the right recline..
With the seat on top of the crank hole.. Use the crank hole for a cross bar to mount training wheels that would also steer.. Leave the rear fork, to attach extention to the frame to the rear wheel.. Steering is a cable shev drive.. X the cable to get the reverse desired steering.. Twice around each pully gives a capson type grip so the cable wont slip and put the fork out of line..

Alright!! Glad to have your company Unjon, my head hurts too! You're coming up with something very interesting it sounds like. To think we've been riding bikes since before we could read (in my case anyways) and now finally get to digging into WHY they work...

Tiahaar wrote:Alright!! Glad to have your company Unjon, my head hurts too! You're coming up with something very interesting it sounds like. To think we've been riding bikes since before we could read (in my case anyways) and now finally get to digging into WHY they work...

Unjon mumbles on his way back to the dark corners.. "no more new projects no more new projects""get out of my head"

I used to have a big yellow sticky-note just below the screen on the puter, that said "NO MORE!" in bright red and yellow yetters.

Didn't work, of course!

Methinks many of us tend to get carried away with/by new ideas. I certainly can bring only a small precentage of them to fruition! But if all these ideas stopped popping up, I think life would be rather dull.

Let's see.... The Firecracker Bike is still only a concept -- and a jar of .38 primers, and a pack of small box matches, and two bricks of firecrackers, and the telescoping seat post that seems made for the purpose.
Next will be the Backwards Bike -- with the chain in a figure-8.
Right now... I gotta earn a living.

most of which can be airily ignored for the purposes of crazy playa bikes

Damn you Tiahaar, I'll get ya for this.. Been up sence 4:00 this morning trying to make the steering design.. It's wont get out of my head..Like when a song sticks.. Went to the parts shed for some flea market stuff.. Ended up wasting two hours mocking up a bike frame and extention bars..

Anyway, The down tube of a stepthru trick bike makes the right recline.. With the seat on top of the crank hole.. Use the crank hole for a cross bar to mount training wheels that would also steer.. Leave the rear fork, to attach extention to the frame to the rear wheel.. Steering is a cable shev drive.. X the cable to get the reverse desired steering.. Twice around each pully gives a capson type grip so the cable wont slip and put the fork out of line..

Cable-on-sheave (pulley) steering is common in KSR. No need to rely on capstan type friction, as the ends of the cable can be fastened securely. Typically, the steering wheel, or crank, has a small-diameter pulley with many turns of cable; and the fork has a large pulley (often made from a bicycle wheel rim) that may even be less than 360 degrees. Works very well, and can be adapted to any layout with small idler pulleys here and there as needed for cable routing. Allows deep down-gearing of steering effort, and also allows wider steering movement than most linkages.

Unjon, the bottom line seems to be that there ARE NO total experts on these matters!

No, a rear-steering wheel can perfectly well have a steering "head" up above it, just like a normal bike has at the front. You'll see it all the time in KSR -- it's just that those vehicles invariably have two wheels up front. The best known example is Duane Flatmo's four-person fire-breathing scrap-aluminum dragon with the moving head that was on the Playa the last two years. Even Bob Thompson's red-white-and-blue machine has a steering head right on top of the seven-foot-tall tail-wheel. Both use cable-on-sheave steering. (Although Bob has used a complicated linkage previously.)

Just picked up two tiny kids bike.. (free from craig's list).. The rear of one of them could be mounted on a articulated frame faceing forward.. The rider would have the drive wheel between his legs.. The peddel and drive wheel could lean with the rear steering..

Okay, I've had two thoughts to toss out to the mechanically devious...

a) an "automatic transmission" - every 'x' revolutions of the the cranks would cause the gearing to change one position?

or

b) after 'x' revolutions the cranks would either lock or spin free. The bike would still roll, but you couldn't pedal any longer?

Hmm, or maybe three thoughts...

Going back to catching the crooks... how about inside the seat (with a porous covering of course) putting a sponge soaked with a bio-luminous substance... after the theft just look for the person with the glowing buttocks!

B. I think I figured this out before. We'd install a second chain on the left side. The left crank sprocket would have ONE tooth more than the right. For each revolution, one tooth's worth of slack would be pulled out of the right chain. When the drailer/tensioner could go no further, the system would bind up.
That's not a complete design, but you get the idea.

3. Too many glowing butts in BRC already. (Or some such wisecrack.):lol:

B. I think I figured this out before. We'd install a second chain on the left side. The left crank sprocket would have ONE tooth more than the right. For each revolution, one tooth's worth of slack would be pulled out of the right chain. When the drailer/tensioner could go no further, the system would bind up. That's not a complete design, but you get the idea.

3. Too many glowing butts in BRC already. (Or some such wisecrack.):lol:

I am thinking there would be enough torque with only 1 tooths difference to part one of the chains. Simple enough to try out though,

I think it is best to go in a group at night. Since there was a person/persons stealing bikes by cutting locks this year, everyone in your group locks as many bikes together as possible. Make it very difficult for anyone to cut a lock and make off with a bike.